This invention relates to gaskets for the joinder of pipes, particularly to features provided in such a gasket for centering the gasket in a flanged pipe joint.
It is well known to be desirable, in fluid piping systems, to provide a smooth fluid path. Non-smooth surfaces increase flow resistance and trap fluid and particulate matter which would otherwise be easily flushed out of the system. This is particularly important when carrying ultra-pure materials. Protrusions and recesses alike trap bacteria or contaminants which may be released unexpectedly and undesirably at later times. In ultra-pure piping systems, contaminants in the parts per billion range may be unacceptable. Such low levels of contamination generally require extremely small surface irregularities in pipe. Concern for this can be so great that, for example, the piping pore size may be regularly inspected using scanning electron microscopy and the pipe joint rejected if the pore size is greater than a maximum allowable value. On account of the fitting together of two different sections of pipe, however, the pipe joint makes an important contribution to the problem of contaminant trapping. Moreover, the quality of this fitting cannot easily be inspected.
In particular, sections of pipe are joined with gaskets. This is because pipe flanges are formed of relatively rigid materials so that they may carry tightening forces. Pipe flange surfaces are not completely smooth or flat, and pipes are not perfectly aligned. Therefore, pipe flanges may not generally be joined in a leak-proof manner without the aid of the relatively compliant, mediating gasket. Within limits, the gasket conforms to the surface quality and angular presentation of the flange surfaces to accommodate any mis-match therebetween, to seal them.
The gasket ideally has an aperture conforming to the inner periphery of the pipe flanges, and extends radially outwardly along the interior surfaces of the pipe flanges. Typical prior art gaskets include holes through which bolts for tightening the joint are passed. The holes are larger than the bolts to ease their installation. However, the holes also provide for locating the gasket with respect to the inner periphery of the pipe flanges. It is not possible, therefore, to position the aperture to be precisely congruent with the inner periphery of the flanges.
The aperture is, typically, made xe2x80x9con-sizexe2x80x9d, i.e., so that the diameter of the aperture is about equal to the diameter of the inner periphery of the flanges. Since registration of the aperture with the inner periphery of the flanges is not perfect, however, the gasket generally protrudes into the stream of fluid flow in some places, and recesses from the inner surfaces of the pipe flanges in other places. Moreover, such traps cannot be avoided by making the gasket over or under-sized.
Accordingly, there is a need for a gasket having centering features that provide for improved centering the gasket in a flanged pipe joint, to decrease flow resistance and the propensity to trap fluid and particulate matter.
The present invention solves the aforementioned problems and meets the aforementioned need by providing, for use in a pipe joint comprising two pipe flanges, each pipe flange being defined by an outer diameter and an inner diameter, and including respective flange faces, outer peripheral surfaces, and inner peripheral surfaces for conducting fluid through the joint, a gasket having centering features adapted for placement of the gasket between the flange faces.
The gasket includes one or more centering portions for centering the gasket radially between the faces of the pipe flange. The centering portions are generally switchable between two configurations: a flush configuration and a centering configuration. The flush configuration permits selecting centering portions for non-use where such centering portions correspond to a size of pipe flange for which the gasket is not being employed.
The centering portions include associated centering edges adapted for making contact with the outer peripheral surface of a selected one of the flanges. The gasket is moved radially between the flange faces until the centering edge of the centering portion abuts the outer peripheral surface. The centering portion is pre-positioned for a given outer diameter of the pipe flange for centering the gasket along an associated radial line.
In a first embodiment of the invention, the centering portion includes a flap element which normally lies flush with the gasket. The flap element can be pressed out of the plane of the gasket to ready the associated centering edge for contact with the pipe flange. In a second embodiment of the invention, the centering portion includes a protuberance which extends from one side of the gasket. The protuberance contains an associated centering edge on a side thereof. The centering portion also includes a cavity in the other side of the gasket which is associated with the protuberance so that pressing the protuberance into the plane of the gasket and into the cavity places the centering portion in its flush configuration, wherein the protuberance becomes substantially flush with the gasket. In a third embodiment of the invention, the centering portion includes a protuberance which extends from one or both sides of the gasket. Removing the protuberance from the gasket places the centering portion in its flush configuration. In a fourth embodiment of the invention, the centering portion comprises an annular ring adapted for mating with an annular relief formed in a corresponding one of the flange faces.
Accordingly, it is a principal object of the present invention to provide a novel gasket having centering features.
It is another object of the present invention to provide such a gasket that decreases flow resistance and the propensity to trap fluid and particulate matter.
It is still another object of the present invention to provide such a gasket that provides for improved centering of a gasket in a flanged pipe joint.
It is yet another object of the present invention to provide such a gasket that provides for adjustment to accommodate different sizes of pipe flanges.
The foregoing and other objects, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the following drawings.